1. Field of the Invention
This invention relates to new polyurethaneurea compositions comprising polymeric glycols and poly(tetramethylene-co-ethyleneether) glycols comprising constituent units derived by copolymerizing tetrahydrofuran and ethylene oxide, wherein the portion of the units derived from ethylene oxide is present in the poly(tetramethylene-co-ethyleneether) glycol from greater than about 37 to about 70 mole percent. The invention further relates to the use of these blends of polymeric glycols and poly(tetramethylene-co-ethyleneether) glycols as the soft segment base material in spandex compositions. The invention also relates to new polyurethane compositions comprising blends of polymeric glycols and poly(tetramethylene-co-ethyleneether) glycols, and their use in spandex.
2. Description of the Related Art
Poly(tetramethylene ether) glycols, also known as polytetrahydrofuran or homopolymers of tetrahydrofuran (THF, oxolane) are well known for their use in soft segments in polyurethaneureas. Poly(tetramethylene ether) glycols impart superior dynamic properties to polyurethaneurea elastomers and fibers. They possess very low glass transition temperatures, but have crystalline melt temperatures above room temperature. Thus, they are waxy solids at ambient temperatures and need to be kept at elevated temperatures to prevent solidification.
Copolymerization with a cyclic ether has been used to reduce the crystallinity of the polytetramethylene ether chains. This lowers the polymer melt temperature of the copolyether glycol and at the same time improves certain dynamic properties of the polyurethaneurea that contains such a copolymer as a soft segment. Among the comonomers used for this purpose is ethylene oxide, which can lower the copolymer melt temperature to below ambient, depending on the comonomer content. Use of poly(tetramethylene-co-ethyleneether) glycols may also improve certain dynamic properties of polyurethaneureas, such as elongation at break and low temperature performance, which is desirable for some end uses.
Poly(tetramethylene-co-ethyleneether) glycols are known in the art. Their preparation is described in U.S. Pat. Nos. 4,139,567 and 4,153,786. Such copolymers can be prepared by any of the known methods of cyclic ether polymerization, such as those described in “Polytetrahydrofuran” by P. Dreyfuss (Gordon & Breach, N.Y. 1982), for example. Such polymerization methods include catalysis by strong proton or Lewis acids, heteropoly acids, and perfluorosulfonic acids or acid resins. In some instances it may be advantageous to use a polymerization promoter, such as a carboxylic acid anhydride, as described in U.S. Pat. No. 4,163,115. In these cases, the primary polymer products are diesters, which then need to be hydrolyzed in a subsequent step to obtain the desired polymeric glycols.
Poly(tetramethylene-co-ethyleneether) glycols offer advantages over poly(tetramethylene ether) glycols in terms of certain specific physical properties. At ethyleneether contents above 20 mole percent, the poly(tetramethylene-co-ethyleneether) glycols are moderately viscous liquids at room temperature and have a lower viscosity than poly(tetramethylene ether) glycols of the same molecular weight at temperatures above the melting point of poly(tetramethylene ether) glycols. Certain physical properties of the polyurethanes or polyurethaneureas prepared from poly(tetramethylene-co-ethyleneether) glycols surpass the properties of those polyurethanes or polyurethaneureas prepared from poly(tetramethylene ether) glycols.
Spandex based on poly(tetramethylene-co-ethyleneether) glycols is also known in the art. However, most of these are based on poly(tetramethylene-co-ethyleneether) containing co-extenders or extenders other than ethylene diamine. For example, U.S. Pat. No. 4,224,432 to Pechhold et al. discloses the use of poly(tetramethylene-co-ethyleneether) glycols with low cyclic ether content to prepare spandex and other polyurethaneureas. Pechhold teaches that ethyleneether levels above 30 percent are preferred. Pechhold does not teach the use of coextenders, though it discloses that mixtures of amines may be used.
U.S. Pat. No. 4,658,065 to Aoshima et al. discloses the preparation of several THF copolyethers via the reaction of THF and polyhydric alcohols using heteropolyacid catalysts. Aoshima also discloses that copolymerizable cyclic ethers, such as ethylene oxide, may be included with the THF in the polymerization process. Aoshima discloses that the copolyether glycols may be used to prepare spandex, but contains no examples of spandex from poly(tetramethylene-co-ethyleneether) glycols.
U.S. Pat. No. 3,425,999 to Axelrood et al. discloses the preparation of polyether urethaneureas from poly(tetramethylene-co-ethyleneether) glycols for use in oil resistance and good low temperature performance. The poly(tetramethylene-co-ethyleneether) glycols have ethyleneether content ranging from 20 to 60 percent by weight (equivalent to 29 to 71 mole percent). Axelrood does not disclose the use of these urethaneureas in spandex.
U.S. Pat. No. 6,639,041 to Nishikawa et al. discloses fibers having good elasticity at low temperature that contain polyurethaneureas prepared from polyols containing copolyethers of THF, ethylene oxide, and/or propylene oxide, diisocyanates, and diamines and polymers solvated in organic solvents. Nishikawa teaches that these compositions have improved low temperature performance over standard homopolymer spandexes. Nishikawa also teaches that “above about 37 mole % ethyleneether content in the copolyether glycol, unload power at low elongations is unacceptably low, elongation-at-break declines, and set rises, though very slightly.” The examples in Nishikawa show that as the mole percent of ethylene ether moiety in the copolyether increases from 22 to 31 to 37 mole percent, the elongation at break rises, but upon increasing to 50 mole percent, the elongation at break then drops.
Due to the lower raw material cost of ethylene oxide and a higher yielding process, the cost of manufacture of poly(tetramethylene-co-ethyleneether) glycol decreases significantly as the ethyleneether content rises. For those spandex composition based on lower ethyleneether content (16 to 35 mole percent ethyleneether) poly(tetramethylene-co-ethyleneether) glycols, this invention provides for lower raw material costs because the cost of a blend of a high ethyleneether content poly(tetramethylene-co-ethyleneether) with poly(tetramethylene ether) glycols is less than the cost of a lower ethyleneether content poly(tetramethylene-co-ethyleneether) glycol.
In addition, it is apparent that high ethyleneether content poly(tetramethylene-co-ethyleneether) glycols are of value for certain spandex end uses while lower ethyleneether content poly(tetramethylene-co-ethyleneether) glycols are of more value for other spandex end uses. This invention allows for the production of only one or two high-ethyleneether copolyether glycols for all spandex end uses. For spandex end uses where a lower ethyleneether-content copolyether glycol is desired, the copolyether glycol could be produced by blending a high ethyleneether poly(tetramethylene-co-ethyleneether) glycol with poly(tetramethylene ether) glycols to reach the target ethyleneether content without sacrificing any of the desired physical properties of the spandex.